The teacher, a participant observer in the total communication environment of the classroom, can, through systematic observation of that communication, attempt a change in behaviors which will result in an improved teaching-learning environment. One systematic way of looking at classroom communication involves the distinction between the nature of communication behaviors--" substance"--and the shifts from one kind of behavior to another another--"transitions." Further dimensions of the "substance" of verbal communication are 1) institutional events, which relate to managing of the classroom and meeting the expectations of the school; 2) task events, which focus on the teaching and learning of subject matter content; and 3) personal events, in which personal goals, needs, or emotions provide the central focus. Further breakdowns can be made, e.g., in the substance of content communication, of classroom questions, and of teacher appraisal behaviors. At times events are "mixed," as when the teacher considers an event a task event while students perceive it as an institutional event. Communication is facilitated when a congruence of the interpretation of the event exists between the communicators. "Transitions" in communication behaviors are as yet a very little explored subject. Teachers employ them of various kinds and complexity for effective explanation of content, management and control, appraisal of student behavior, and other purposes. (JS)